Mechanism of eletrophillic chlorination: experimental determination of a geometrical requirement for chlorine transfer by the endocyclic restriction test

An endocyclic restriction test for acid-catalyzed transfer of chlorine from a protonated chloromine to an aromatic ring provides data that are consistent with a transition structure with a large bond angle between the entering and leaving groups around chlorine. The results rule a mechanism that has an oblique angle between the entering and leaving groups.